Seasonal impact of mineral dust on deep-ocean particle flux in the easternsubtropical Atlantic Ocean

Seasonal lithogenic particle and Al fluxes were obtained from a deep-ocean sediment trap deployment during 1992 and 1993 off NW Africa, and were compa red concurrently with atmospheric Al concentrations and two-dimensional bac kward trajectories of windfields from two barometric levels in the lower an d mid troposphere. Marine Al fluxes, lithogenic particle fluxes and grain s ize distributions in the area were found to be directly linked to airmass p athways and surface mineral aerosol concentrations. At 1000 m water depth, highest Al fluxes (10.77 mg m(-2) day(-1)), lithogenic particle fluxes (99. 25 mg m(-2) day(-1)) and smallest mean grain sizes (11.9 mu m) occurred dur ing the winter and spring season, concurrent with highest atmospheric dust load and Al-concentrations (15 300 ng m(-3)) in the lower troposphere. A st rong seasonal change of the main atmospheric dust transport from low altitu de winds during winter/spring to higher altitudes during summer is clearly reflected at depth by a significant coarsening of mean grain sizes (18.6 mu m) and lowest Al (0.81 mg m(-2) day(-1)) and lithogenic particle fluxes (1 1.3 mg m(-2) day(-1)) found in the sediment traps. The comparison of marine , atmospheric and model derived data used within this study highlights the close temporal coupling between atmospheric dust transport and the deep-oce an particle stock. (C) 1999 Elsevier Science B.V. All rights reserved.